INVESTIGATIONS RELATED TO THE OPPORTUNITY OF USING FURNACE SLAG IN THE COMPOSITION OF ROAD CEMENT CONCRETE

Abstract

BFS blast furnace slag presentation of the challenges and opportunities is related to the use as a substitute of Portland cement, respectively of natural sand in the composition of road cement concretes. The inclusion of BFS in the composition of road concrete is an ecological approach from the point of view of reducing the consumption of non-renewable materials. A rational design of road concrete composition requires knowledge of the physical-mechanical properties of BSF with favorable and unfavorable impact on the durability of road concrete. Aspects of the impact of the quality of GGBS granulated and ground blast furnace slag as well as the properties of ACBFS air-cooled blast furnace slag crushed aggregates were analyzed in this article. Although all the physical-mechanical properties books are suitable for the slag powders inclusion in the road concretes composition, the high content of CaO-free and C3A limits the substitution of cement with GGBS to prevent the occurrence of degradation during the exploitation period. ACBFS aggregates have been proven to be non-reactive to alkalis in cement, thus being suitable for inclusion in road cement concrete compositions. The increased values of the water absorption coefficient, respectively of the fineness modulus of the ACBFS type aggregates compared to natural sand, the reduction of the workability of the road concrete and the increase of the water/binder ratio. Finally, for the design of road concrete compositions with slag, preliminary tests were carried out on three series of mixtures, in which Portland cement was replaced by 15% GGBS and natural sand by 25% and 50% ACBFS respectively. The optimal slag road concrete recipe was established based in: increased workability (an important characteristic of road concretes), a low water/binder ratio and a 7-day compressive strength close to the control sample.

Keywords

• road concrete with slag
• the oxide composition
• activity index
• mortar microstructure
• water absorption coefficient
• workability
• compression strength